/* See COPYRIGHT for copyright information. */

#include <inc/x86.h>
#include <inc/error.h>
#include <inc/string.h>
#include <inc/assert.h>

#include <kern/env.h>
#include <kern/pmap.h>
#include <kern/trap.h>
#include <kern/syscall.h>
#include <kern/console.h>
#include <kern/sched.h>
#include <kern/time.h>
#include <kern/e100.h>

// Print a string to the system console.
// The string is exactly 'len' characters long.
// Destroys the environment on memory errors.
static void
sys_cputs(const char *s, size_t len)
{
	// Check that the user has permission to read memory [s, s+len).
	// Destroy the environment if not.
    user_mem_assert(curenv, s, len, PTE_P); 
    cprintf("%.*s", len, s);
}

// Read a character from the system console without blocking.
// Returns the character, or 0 if there is no input waiting.
static int
sys_cgetc(void)
{
	return cons_getc();
}

// Returns the current environment's envid.
static envid_t
sys_getenvid(void)
{
	return curenv->env_id;
}

// Destroy a given environment (possibly the currently running environment).
//
// Returns 0 on success, < 0 on error.  Errors are:
//	-E_BAD_ENV if environment envid doesn't currently exist,
//		or the caller doesn't have permission to change envid.
static int
sys_env_destroy(envid_t envid)
{
	int r;
	struct Env *e;

	if ((r = envid2env(envid, &e, 1)) < 0)
		return r;
	env_destroy(e);
	return 0;
}

// Deschedule current environment and pick a different one to run.
static void
sys_yield(void)
{
	sched_yield();
}

// Allocate a new environment.
// Returns envid of new environment, or < 0 on error.  Errors are:
//	-E_NO_FREE_ENV if no free environment is available.
//	-E_NO_MEM on memory exhaustion.
static envid_t
sys_exofork(void)
{
	// Create the new environment with env_alloc(), from kern/env.c.
	// It should be left as env_alloc created it, except that
	// status is set to ENV_NOT_RUNNABLE, and the register set is copied
	// from the current environment -- but tweaked so sys_exofork
	// will appear to return 0.

	// LAB 4: Your code here.
    struct Env *newEnv  = NULL;
    int i,r;
    if (!(r=env_alloc(&newEnv, curenv->env_id))) {
      newEnv->env_tf                  = curenv->env_tf;
      newEnv->env_tf.tf_regs.reg_eax  = 0;
      newEnv->env_status              = ENV_NOT_RUNNABLE;
    } else
      panic("Failed: %e", r);
    return newEnv->env_id;
}

// Set envid's env_status to status, which must be ENV_RUNNABLE
// or ENV_NOT_RUNNABLE.
//
// Returns 0 on success, < 0 on error.  Errors are:
//	-E_BAD_ENV if environment envid doesn't currently exist,
//		or the caller doesn't have permission to change envid.
//	-E_INVAL if status is not a valid status for an environment.
static int
sys_env_set_status(envid_t envid, int status)
{
	// Hint: Use the 'envid2env' function from kern/env.c to translate an
	// envid to a struct Env.
	// You should set envid2env's third argument to 1, which will
	// check whether the current environment has permission to set
	// envid's status.

	// LAB 4: Your code here.
    struct Env *env = NULL;
    
    if (status!=ENV_RUNNABLE && status!=ENV_NOT_RUNNABLE) {
        return -E_INVAL;
    }

    if (!envid2env(envid, &env, 1)) {
        env->env_status = status;
        return 0;
    }
    return -E_BAD_ENV;
}

// Set envid's trap frame to 'tf'.
// tf is modified to make sure that user environments always run at code
// protection level 3 (CPL 3) with interrupts enabled.
//
// Returns 0 on success, < 0 on error.  Errors are:
//	-E_BAD_ENV if environment envid doesn't currently exist,
//		or the caller doesn't have permission to change envid.
static int
sys_env_set_trapframe(envid_t envid, struct Trapframe *tf)
{
	// LAB 5: Your code here.
	// Remember to check whether the user has supplied us with a good
	// address!
    struct Env *e   = NULL;
    int r   = 0;
    if (tf==NULL||(((uint32_t)tf)>USTACKTOP))
        return -E_INVAL;

    if ((r=envid2env(envid, &e, 1)<0))
        return r;

    e->env_tf   = *tf;
    return 0;
}

// Set the page fault upcall for 'envid' by modifying the corresponding struct
// Env's 'env_pgfault_upcall' field.  When 'envid' causes a page fault, the
// kernel will push a fault record onto the exception stack, then branch to
// 'func'.
//
// Returns 0 on success, < 0 on error.  Errors are:
//	-E_BAD_ENV if environment envid doesn't currently exist,
//		or the caller doesn't have permission to change envid.
static int
sys_env_set_pgfault_upcall(envid_t envid, void *func)
{
    struct Env *env = NULL;

    if (!envid2env(envid, &env, 1)) {
        env->env_pgfault_upcall = func;
        return 0;
    }
    return -E_BAD_ENV;
}

// Allocate a page of memory and map it at 'va' with permission
// 'perm' in the address space of 'envid'.
// The page's contents are set to 0.
// If a page is already mapped at 'va', that page is unmapped as a
// side effect.
//
// perm -- PTE_U | PTE_P must be set, PTE_AVAIL | PTE_W may or may not be set,
//         but no other bits may be set.  See PTE_USER in inc/mmu.h.
//
// Return 0 on success, < 0 on error.  Errors are:
//	-E_BAD_ENV if environment envid doesn't currently exist,
//		or the caller doesn't have permission to change envid.
//	-E_INVAL if va >= UTOP, or va is not page-aligned.
//	-E_INVAL if perm is inappropriate (see above).
//	-E_NO_MEM if there's no memory to allocate the new page,
//		or to allocate any necessary page tables.
static int
sys_page_alloc(envid_t envid, void *va, int perm)
{
	// Hint: This function is a wrapper around page_alloc() and
	//   page_insert() from kern/pmap.c.
	//   Most of the new code you write should be to check the
	//   parameters for correctness.
	//   If page_insert() fails, remember to free the page you
	//   allocated!
  struct Page *newPage    = NULL;
  struct Env *env         = NULL;

  // Check if permissions are valid.
  if ((perm & (PTE_U|PTE_P)) != (PTE_U|PTE_P))
    return -E_INVAL;

  // Check if va is valid.
  if (((uint32_t)va >= UTOP)
    || ((uint32_t)va & 0xFFF))
    return -E_INVAL;

  // Check if request is from a privileged environment.
  if (envid2env(envid, &env, 1))
    return -E_BAD_ENV;

  // Allocate Page Here.
  if (!(page_alloc(&newPage))) {
    memset(newPage, 0, sizeof(struct Page));
    memset(page2kva(newPage), 0, PGSIZE);
    if (page_insert(env->env_pgdir, newPage, va, perm)) {
        page_free(newPage);
        return -E_NO_MEM;
    }
    return 0;
  } else
    return -E_NO_MEM;
  return -E_INVAL;
}

// Map the page of memory at 'srcva' in srcenvid's address space
// at 'dstva' in dstenvid's address space with permission 'perm'.
// Perm has the same restrictions as in sys_page_alloc, except
// that it also must not grant write access to a read-only
// page.
//
// Return 0 on success, < 0 on error.  Errors are:
//	-E_BAD_ENV if srcenvid and/or dstenvid doesn't currently exist,
//		or the caller doesn't have permission to change one of them.
//	-E_INVAL if srcva >= UTOP or srcva is not page-aligned,
//		or dstva >= UTOP or dstva is not page-aligned.
//	-E_INVAL is srcva is not mapped in srcenvid's address space.
//	-E_INVAL if perm is inappropriate (see sys_page_alloc).
//	-E_INVAL if (perm & PTE_W), but srcva is read-only in srcenvid's
//		address space.
//	-E_NO_MEM if there's no memory to allocate any necessary page tables.
static int
sys_page_map(envid_t srcenvid, void *srcva,
	     envid_t dstenvid, void *dstva, int perm)
{
	// Hint: This function is a wrapper around page_lookup() and
	//   page_insert() from kern/pmap.c.
	//   Again, most of the new code you write should be to check the
	//   parameters for correctness.
	//   Use the third argument to page_lookup() to
	//   check the current permissions on the page.
    struct Env *srcEnv      = NULL;
    struct Env *dstEnv      = NULL;
    pte_t *srcPte           = NULL;
    struct Page *page       = NULL;

    // Check if permissions are valid.
    if ((perm & (PTE_U|PTE_P)) != (PTE_U|PTE_P)) {
        return -E_INVAL;
    }

    // Check if va is valid.
    if (((uint32_t)srcva >= UTOP)
        || ((uint32_t)dstva >= UTOP))
        return -E_INVAL;

    // Check if request is from a privileged environment.
    if (envid2env(srcenvid, &srcEnv, 1) || envid2env(dstenvid, &dstEnv, 1)) {
        return -E_BAD_ENV;
    }

    if ((page=page_lookup(srcEnv->env_pgdir, srcva, &srcPte))) {
      if ((perm & PTE_W) && ((*srcPte & PTE_W) == 0))
        return -E_INVAL;
      return page_insert(dstEnv->env_pgdir, page, dstva, perm);
    }
    return -E_INVAL;
}

// Unmap the page of memory at 'va' in the address space of 'envid'.
// If no page is mapped, the function silently succeeds.
//
// Return 0 on success, < 0 on error.  Errors are:
//	-E_BAD_ENV if environment envid doesn't currently exist,
//		or the caller doesn't have permission to change envid.
//	-E_INVAL if va >= UTOP, or va is not page-aligned.
static int
sys_page_unmap(envid_t envid, void *va)
{
	// Hint: This function is a wrapper around page_remove().
    struct Env *env = NULL;

    // Check if va is valid.
    if (((uint32_t)va >= UTOP)
        || ((uint32_t)va & 0xFFF))
        return -E_INVAL;

    // Check if request is from a privileged environment.
    if (envid2env(envid, &env, 1))
      return -E_BAD_ENV;

    page_remove(env->env_pgdir, va);
    return 0;
}

// Try to send 'value' to the target env 'envid'.
// If srcva < UTOP, then also send page currently mapped at 'srcva',
// so that receiver gets a duplicate mapping of the same page.
//
// The send fails with a return value of -E_IPC_NOT_RECV if the
// target is not blocked, waiting for an IPC.
//
// The send also can fail for the other reasons listed below.
//
// Otherwise, the send succeeds, and the target's ipc fields are
// updated as follows:
//    env_ipc_recving is set to 0 to block future sends;
//    env_ipc_from is set to the sending envid;
//    env_ipc_value is set to the 'value' parameter;
//    env_ipc_perm is set to 'perm' if a page was transferred, 0 otherwise.
// The target environment is marked runnable again, returning 0
// from the paused sys_ipc_recv system call.  (Hint: does the
// sys_ipc_recv function ever actually return?)
//
// If the sender wants to send a page but the receiver isn't asking for one,
// then no page mapping is transferred, but no error occurs.
// The ipc only happens when no errors occur.
//
// Returns 0 on success, < 0 on error.
// Errors are:
//	-E_BAD_ENV if environment envid doesn't currently exist.
//		(No need to check permissions.)
//	-E_IPC_NOT_RECV if envid is not currently blocked in sys_ipc_recv,
//		or another environment managed to send first.
//	-E_INVAL if srcva < UTOP but srcva is not page-aligned.
//	-E_INVAL if srcva < UTOP and perm is inappropriate
//		(see sys_page_alloc).
//	-E_INVAL if srcva < UTOP but srcva is not mapped in the caller's
//		address space.
//	-E_INVAL if (perm & PTE_W), but srcva is read-only in the
//		current environment's address space.
//	-E_NO_MEM if there's not enough memory to map srcva in envid's
//		address space.
static int
sys_ipc_try_send(envid_t envid, uint32_t value, void *srcva, unsigned perm)
{
  struct Env *env = NULL;
  pte_t *pte      = NULL;
  struct Page *pg = NULL;

  if (envid2env(envid, &env, 0)) {
    return -E_BAD_ENV;
  }

  if (env->env_ipc_recving != 1) {
    return -E_IPC_NOT_RECV;
  }

  if (((uint32_t)srcva < UTOP) && 
    ((uint32_t)srcva%PGSIZE == 0) &&
    (pg=page_lookup(curenv->env_pgdir, srcva, &pte)) &&
    (((pte[PTX(srcva)]&PTE_USER)==(pte[PTX(srcva)]&perm)) || (perm==0))) {
    if ((uint32_t)env->env_ipc_dstva < UTOP) {
      if (page_insert(env->env_pgdir, pg, env->env_ipc_dstva, perm)) {
        env->env_ipc_perm   = 0;
        return -E_NO_MEM;
      }
      env->env_ipc_perm   = perm;
    } else {
      env->env_ipc_perm   = 0;
    }
  } else if ((uint32_t)srcva < UTOP) {
    env->env_ipc_perm   = 0;
    return -E_INVAL;
  }
  env->env_ipc_recving    = 0;
  env->env_ipc_dstva      = NULL;
  env->env_ipc_from       = curenv->env_id;
  env->env_ipc_value      = value;
  env->env_status         = ENV_RUNNABLE;
  return 0;
}

// Block until a value is ready.  Record that you want to receive
// using the env_ipc_recving and env_ipc_dstva fields of struct Env,
// mark yourself not runnable, and then give up the CPU.
//
// If 'dstva' is < UTOP, then you are willing to receive a page of data.
// 'dstva' is the virtual address at which the sent page should be mapped.
//
// This function only returns on error, but the system call will eventually
// return 0 on success.
// Return < 0 on error.  Errors are:
//	-E_INVAL if dstva < UTOP but dstva is not page-aligned.
static int
sys_ipc_recv(void *dstva)
{
  if (((uint32_t)dstva < UTOP) && ((uint32_t)dstva%PGSIZE != 0))
    return -E_INVAL;

  curenv->env_ipc_recving = 1;
  curenv->env_ipc_dstva   = dstva;
  curenv->env_status      = ENV_NOT_RUNNABLE;
	return 0;
}

/**
 * This system call is used to transmit packets to the network.
 * It does so by forwarding the send request to the network driver.
 **/

static int
sys_ns_send(void *pkt, int len) {
    int r=0;
    if (!pkt)
        return -E_INVAL;
    
    if ((((uint32_t)pkt)+len)>USTACKTOP)
        return -E_INVAL;

    return e100_ns_send(pkt, len);
}

/**
 * This system call receives packets from the network.
 * It calls an interface to network driver to fetch the 
 * received packet.
 **/

static int
sys_ns_recv(void *pkt, int len) {
    if (!pkt)
        return -E_INVAL;
    
    if ((((uint32_t)pkt)+len)>USTACKTOP)
        return -E_INVAL;

    return e100_ns_recv(pkt, len);
}

// Return the current time.
static int
sys_time_msec(void) 
{
	// LAB 6: Your code here.
    return time_msec();
}

// Dispatches to the correct kernel function, passing the arguments.
int32_t
syscall(uint32_t syscallno, uint32_t a1, uint32_t a2, uint32_t a3, uint32_t a4, uint32_t a5)
{
	// Call the function corresponding to the 'syscallno' parameter.
	// Return any appropriate return value.
	// LAB 3: Your code here.
  switch(syscallno) {
    case SYS_cputs:
      sys_cputs((char *)a1, a2);
      return a2;
    case SYS_cgetc:
      return sys_cgetc();
    case SYS_getenvid:
      return sys_getenvid();
    case SYS_env_destroy:
      return sys_env_destroy((envid_t)a1);
    case SYS_yield:
      sys_yield();
      return 0;
    case SYS_exofork:
      return sys_exofork();
    case SYS_env_set_status:
      return sys_env_set_status((envid_t)a1, (int)a2);
    case SYS_page_alloc:
      return sys_page_alloc((envid_t)a1, (void *)a2, a3);
    case SYS_page_map:
      return sys_page_map((envid_t)a1, (void *)a2, (envid_t)a3, (void *)a4, (int)a5);
    case SYS_page_unmap:
      return sys_page_unmap((envid_t)a1, (void *)a2);
    case SYS_env_set_pgfault_upcall:
      return sys_env_set_pgfault_upcall((envid_t)a1, (void *)a2);
    case SYS_ipc_recv:
      return sys_ipc_recv((void *)a1);
    case SYS_ipc_try_send:
      return sys_ipc_try_send((envid_t)a1, (uint32_t)a2, (void *)a3, a4);
    case SYS_env_set_trapframe:
      return sys_env_set_trapframe((envid_t)a1, (struct Trapframe *)a2);
    case SYS_time_msec:
      return sys_time_msec();
    case SYS_ns_send:
      return sys_ns_send((void *)a1, (int)a2);
    case SYS_ns_recv:
      return sys_ns_recv((void *)a1, (int)a2);
  }
	panic("syscall not implemented");
}

